2.1 Backhaul Network, Tiers and Costs
Mobile backhaul (MBH) networks serve mobile networks by providing connections between mobile network elements located in different geographical sites; no mobile network exists without a related MBH network. The main task of a MBH network is to connect a very large number of mobile network base station sites to a relatively small number of central sites where the mobile network core elements are located.
Basically a MBH network transfers transparently mobile system internal traffic and signaling between the mobile system elements. Even if mobile traffic is not interpreted by the MBH network, its properties affect mobile traffic in several ways, and thus the MBH network has a significant influence on the mobile network end-to-end quality. It is important to take these dependencies and influence fully into account when designing mobile networks which are optimized in respect of total cost and end-to-end performance.
To give some idea of the MBH network overall structure, one can note that a mobile network typically contains thousands, sometimes even tens of thousands, of base station sites (cell sites) while the number of core sites varies from 2 to 10 sites in smaller networks and is up to some tens in very large networks. In addition there is often, depending on the geographical area covered and on the operator network strategy, a number of intermediate sites, where some concentrating mobile network elements are located (typically BSCs, RNCs ...